34 struct Data {  struct
43   Data(StreamID stream_id,  in Data()  function
64   Data& operator=(Data&& other) = default;  argument
67   Data Clone() const {  in Clone()  argument
73   size_t size() const { return payload.size(); }  in size()
76   StreamID stream_id;
80   SSN ssn;
85   MID message_id;
87   FSN fsn;
90   PPID ppid;
93   std::vector<uint8_t> payload;
96   IsBeginning is_beginning;
97   IsEnd is_end;
99   IsUnordered is_unordered;